Square root of leetcode 69. x

Their thinking

Dichotomy （left, middle, right）, With left > right Is a termination condition
Consider special circumstances ：left == right Also enter when while loop , here middle*middle == x（ Or because of decimals middle*middle <= x）, First use ans Save the results , The next entry into the cycle does not meet the conditions .

C++ Code

class Solution {
    
public:
    int mySqrt(int x) 
    {
    
        int left = 0, right = x, ans=-1;
        while (left <= right)
        {
    
            int middle = (left+ right)/2;
            if ((long long)middle*middle <= x)
            {
    
                ans = middle;// in order to middle*middle==x, Directly jump out of the loop 
                left = middle + 1;
            }

            else 
            {
    
                right = middle - 1;
            }
       
        }
        return ans;
    }
};

The two methods originally used ： Violence law , And not used left > right The dichotomy of this judgment condition